Cooling Device for Installation in an Aircraft

ABSTRACT

The present invention relates to a cooling device ( 20 ) for installation in an aircraft, in particular a passenger aircraft. The cooling device ( 20 ) comprises a heat exchanger ( 26 ) configured for flow-through of a liquid coolant for pre-cooling a cooling chamber ( 34 ) of the cooling device ( 20 ) to a temperature of the liquid coolant, the heat exchanger ( 26 ) being coupled in a heat-transferring manner to a refrigerant ( 28 ) which is in thermal contact with the cooling chamber ( 34 ) of the cooling device ( 20 ) for cooling the cooling chamber ( 34 ) to a temperature which is below the temperature of the liquid coolant, wherein the heat exchanger ( 26 ) and the refrigerant ( 28 ) are disposed inside the cooling chamber ( 34 ) of the cooling device ( 20 ), and wherein the heat exchanger ( 26 ) is configured for connection to a liquid coolant supply system installed on board the aircraft.

FIELD OF THE INVENTION

The present invention relates to a cooling device for installation in anaircraft, in particular a passenger aircraft.

BACKGROUND OF THE INVENTION

Certain food, such as, for example, fish or ice cream, must be cooled orkept frozen, in particular on long-distance flights, until it isprepared for consumption. This relates not only to food, but also tomedicines or other pharmaceutical preparations which are intended as anemergency supply for the passengers.

Cooling appliances are provided for cooling or freezing on board apassenger aircraft, these normally being connected to the electricalpower supply of the aircraft. These cooling appliances operate accordingto the known principle of a refrigeration cycle process. In a process ofthis kind the coolant cyclically changes its state of aggregation fromliquid to gaseous and back. When the state of aggregation changes fromliquid to gaseous, the coolant absorbs thermal energy, whereas itreleases thermal energy when a change takes place from gaseous toliquid. A schematic representation of a conventional compression-typerefrigerating machine is shown in FIG. 1.

In a conventional compression-type refrigerating machine 10 the gaseousrefrigerant is firstly compressed by a compressor 19. It is subsequentlycondensed (liquefied), while releasing heat, in a condenser 17. A nozzle16 causes the liquefied refrigerant to expand, this being evaporated,while absorbing heat, in an evaporator 14. Due to the cooling capacityprovided by the evaporator 14, heat is removed from the air in a coolingcompartment 11. The cycle is now concluded and can recommence in thecompressor 19. Energy must be supplied to the compressor 19 from outsidein order to keep this process going.

A fan 15 is used in order to improve the heat transfer as well as thetemperature distribution in the cooling compartment 11. A further fan 18sucks in, through an air inlet 12, outside air which is heated by theheat released by the evaporator 17. This heated air is delivered to theenvironment through the fan 18 via an air outlet 13.

On account of the high number of components required for thecompression-type refrigerating machine which is represented in FIG. 1, arelatively large construction space is necessary, which is ofdisadvantage in particular on board an aircraft. These compression-typerefrigerating machines are also relatively heavy and produce vibrationsand noise on account of the intermittently working compressor. Moreover,the heat which is removed from the cooling compartment 11 is released tothe air surrounding the cooling appliance. Therefore, when installing acooling appliance of this kind in small closed push-in compartments in agalley, a constant air exchange must be guaranteed in order to preventoverheating of the cooling appliance and excessive heating of theenvironment. For this purpose it is necessary to provide a suctionsystem which can only be integrated into the often cramped conditionswith a relatively high constructional expenditure.

WO 2004/071239 A1 discloses a cooling unit for a service trolley for usein an aircraft or train. The cooling unit comprises a Peltier elementlocated inside a heat-insulating material which divides a drawer of thetrolley in a forward cooling section and a rearward intermediate sectiondefined by the rear wall of the drawer and the heat-insulating material.Each end of the Peltier element is connected in a heat-transferringmanner with a heat exchanger. The Peltier element serves to cool thecooling section of the drawer of the service trolley. In each of thecooling section and the intermediate section there is provided a fan forcirculating the relatively warm air in the intermediate section and therelatively cold air in the cooling section. When the service trolley hasbeen parked in a galley of the aircraft, an opening in the rear wall ofthe drawer is aligned with an opening in the wall of the galley. Warmair from the intermediate section of the drawer is circulated throughthe wall opening into a central air circulation system.

A thermoelectric cooling device, in particular for a cooler for anautomobile, is described in DE 36 39 089 A1. The thermoelectric coolingdevice includes at least one Peltier block. The warm side of the Peltierblock is connected in a heat-transferring manner with a first heatexchanger through which a liquid coolant from a liquid coolant supplycircuit is circulated, and the cold side of the Peltier block is inthermal contact with a ribbed recuperator which takes up the entirecross section of a flow channel through which air to be cooled iscirculated. The cooled air is then discharged by means of a fan into thecooling space of the cooler. The liquid coolant supply circuit isprovided with a third heat exchanger for cooling the liquid coolant.Both the first heat exchanger and the ribbed recuperator are disposedoutside the cooling space of the cooler.

The invention is therefore based on the object of providing a coolingdevice for installation in an aircraft which requires littleconstruction space, is easy to install and in the case of which the airsurrounding the cooling device does not have to be exchanged.

SUMMARY OF THE INVENTION

This object is achieved by a cooling device for installation in anaircraft, in particular a passenger aircraft, which comprises a heatexchanger configured for flow-through of a liquid coolant forpre-cooling a cooling chamber of the cooling device to a temperature ofthe liquid coolant, the heat exchanger being coupled in aheat-transferring manner to a refrigerant which is in thermal contactwith the cooling chamber of the cooling device for cooling the coolingchamber (34) to a temperature which is below the temperature of theliquid coolant, wherein the heat exchanger and the refrigerant aredisposed inside the cooling chamber of the cooling device, and whereinthe heat exchanger is configured for connection to a liquid coolantsupply system installed on board the aircraft.

The heat exchanger which is disposed in the cooling device and throughwhich a liquid coolant can flow causes heat to be removed from the airin the cooling chamber of the cooling device and therefore the coolingchamber to be cooled. Since, moreover, a refrigerant which is in thermalcontact with the cooling chamber of the cooling device is coupled in aheat-transferring manner to the heat exchanger, the air in the coolingchamber of the cooling device can be cooled to a temperature which islower than the temperature of the liquid coolant. As the heat exchangeris configured for connection with a liquid coolant supply system whichis installed on board the aircraft, the liquid coolant which is providedby the supply system is used to dissipate the heat which is removed fromthe cooling chamber of the cooling device. It is as a result possible toavoid a suction system which is complicated to install, as is necessaryfor the air exchange in the conventional compression-type refrigeratingmachine. The cooling device can therefore be installed in a space-savingmanner and without a high constructional expenditure in a push-incompartment of a galley. As the heat exchanger and the refrigerant aredisposed inside the cooling chamber of the cooling device, efficientpre-cooling of the air in the cooling chamber of the cooling devicethrough the heat exchanger and even further cooling of the air to belowthe temperature level of the liquid coolant flowing through the heat sexchanger can be achieved. Additionally, a liquid coolant flows throughthe heat exchanger. A liquid coolant has a higher energy density onaccount of its higher thermal capacity. The liquid coolant can as aresult absorb and dissipate more energy (heat) per unit of volume.Moreover, the requirements to be met in terms of tightness of the heatexchanger are lower.

According to one preferred configuration of the invention, therefrigerant is a Peltier element. If the warm side of the Peltierelement is cooled by the heat exchanger through which the liquid coolantcan flow, the cold side of the Peltier element is cooled further,resulting in a large temperature difference between the two sides of thePeltier element, according to the material which is used for the Peltierelement and the applied current. Peltier elements of this kind can beinstalled very easily and in a space-saving manner and require just onepower connection to produce the desired temperature difference.

According to a further preferred embodiment of the invention, the heatexchanger can be connected through an intake and a return for the liquidcoolant to a line system which is installed on board the aircraft. Theline system which is installed on board the aircraft provides the liquidcoolant for the cooling device. The line connections require acomparatively small construction space and the heat is dissipated viathis so-called refrigeration bus. It is as a result possible to installthe cooling device in small compartments which are closed off from theaircraft cabin.

The heat exchanger is preferably formed according to the counterflowprinciple, which results in a further increase in the efficiency of theheat exchanger with regard to its cooling effect.

According to one preferred embodiment of the invention, the heatexchanger comprises a throttle element which throttles the flow volumeof the liquid coolant through the heat exchanger. A specific temperaturecan be set in the cooling chamber of the cooling device through thisthrottle element, which is preferably formed as a control valve.

According to a further configuration of the invention, the throttleelement is disposed in the return.

In addition, according to one preferred embodiment of the invention, afan is disposed in the cooling chamber of the cooling device. This fancirculates the air in the cooling chamber, as a result of which the heattransfer to the refrigerant as well as the heat exchanger is improvedand the temperature distribution in the cooling chamber of the coolingdevice is rendered more homogeneous.

According to a further preferred embodiment of the invention, the liquidcoolant does not undergo a phase transition during operation of thecooling device. The cooling device can thus be operated in a moreenergy-saving manner, as energy is absorbed or released upon each phasetransition, this subsequently being required again in order to againattain the original phase state of the liquid coolant. Moreover, one isform of energy cannot be completely converted into another form ofenergy, so that a cooling system in which the liquid coolant undergoes aphase transition must be supplied with energy from outside after eachcomplete cooling cycle. This additional energy is not required in thecase of the cooling device according to this preferred embodiment.

According to a further configuration of the invention, the heatexchanger and the refrigerant are formed such that the cooling chambercan be cooled to a temperature below 0° C. The cooling device cantherefore be used to freeze food and other products such as, forexample, medicines, which must be available as an emergency supply forthe passengers during a long-distance flight.

The invention is described in the following by way of example on thebasis of a preferred embodiment with reference to schematic drawingswhich represent this preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures:

FIG. 1 represents a conventional compression-type refrigerating machine;

FIG. 2 represents a cooling device according to a preferred embodimentof the invention, and

FIG. 3 depicts a heat exchanger which can be used in the cooling deviceof FIG. 2 and which is configured according to the counterflowprinciple.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The cooling device 20 which is represented in FIG. 2 comprises a coolingchamber 34 in which a heat exchanger 26 and a refrigerant 28, forexample a Peltier element, are disposed. The heat exchanger 26 iscoupled in a heat-transferring manner to the Peltier element 28. Theheat exchanger 26 is connected via an intake 22 and a return 24 to aline system (not shown) which is installed on board the aircraft. Aliquid coolant which is provided by the line system can thus flowthrough the heat exchanger. The temperature of the liquid coolant whichis used in this embodiment typically lies below 0° C.

A throttle element 32, for example a control valve, is disposed in thereturn 24, which element controls the flow volume of the liquid coolantthrough the heat exchanger 26. A fan 30 is in addition provided in thecooling chamber 34 to circulate the air in order to improve the heattransfer to the heat exchanger 26 as well as the refrigerant 28 and toprovide a more homogeneous temperature distribution in the coolingchamber 34 of the cooling device 20.

The heat exchanger 26 through which the liquid coolant can flowguarantees pre-cooling of the air in the cooling chamber 34, while thetemperature level in the cooling chamber 34 can be lowered further bythe Peltier element 28. It is as a result possible to attaintemperatures in the cooling chamber 34 which are sufficient for freezingproducts, for example food or medicines.

As the cooling device 20 comprises an open cooling circuit, the heatwhich is released upon cooling can be dissipated through the liquidcoolant via a refrigeration bus. The cooling device 20 does nottherefore require a refrigerating machine with a closed cooling circuitin which the heat which is generated by the refrigerating machine mustbe dissipated through a separate suction system on account of thechanges of the state of aggregation of the liquid coolant. The lineconnections 22, 24 of the refrigeration bus require only a smallconstruction space when compared with the conventional compression-typerefrigerating machine which is represented in FIG. 1. The cooling device20 can thereby be installed in small compartments which are closed offfrom the aircraft cabin.

FIG. 3 shows a heat exchanger 26′ which can be used in the coolingdevice 20 of

FIG. 2. The heat exchanger 26′ of FIG. 3 is configured according to thecounter-flow principle.

The heat exchanger 26′ comprises an upper conduit through which a liquidcoolant from a liquid coolant supply system installed on board theaircraft flows in one direction (in FIG. 3 from left to right), and asecond conduit through which air to be cooled flows in an oppositedirection (in FIG. 3 from right to left). A Peltier element 28′ islocated in the second conduit and is in thermal contact with the heatexchanger 26′. Means 27′, such as zig-zag arranged portions of metalsheet, are provided in the first conduit in order to avoid, or at leastminimise, any turbulences caused by the flow of liquid coolant throughthe first conduit. Cooling fins 29′ are arranged inside the secondconduit in order to more evenly distribute the cooling power provided bythe Peltier element 28′ and to extend the time period during which theincoming air to be cooled stays within the second conduit. A fan 30′ isalso provided in order to promote air flow through the second conduit,and thus air circulation inside the cooling chamber 34 of the coolingdevice 20 of FIG. 2. The entire assembly shown in FIG. 3 may be disposedwithin the cooling chamber 34 of the cooling device 20 of FIG. 2.Additionally, a throttle element 32, such as a control valve, may bearranged in the return (the right hand side of the first conduit in FIG.3) in order to control the flow volume of the liquid coolant through thefirst conduit of the heat exchanger 26′.

1-10. (canceled)
 11. Cooling device (20) for installation in anaircraft, in particular a passenger aircraft, comprising a heatexchanger (26) configured for flow-through of a liquid coolant forpre-cooling a cooling chamber (34) of the cooling device (20) to atemperature of the liquid coolant, the heat exchanger (26) being coupledin a heat-transferring manner to a refrigerant (28) which is in thermalcontact with the cooling chamber (34) of the cooling device (20) forcooling the cooling chamber (34) to a temperature which is below thetemperature of the liquid coolant, wherein the beat exchanger (26) andthe refrigerant (28) are disposed inside the cooling chamber (34) of thecooling device (20), and wherein the heat exchanger (26) is configuredfor connection to a liquid coolant supply system installed on board theaircraft.
 12. Cooling device according to claim 11, wherein therefrigerant (28) is a Peltier element.
 13. Cooling device according toclaim 11, wherein that the heat exchanger (26) is provided with anintake (22) and a return (24) for the liquid coolant for connection to aline system which is installed on board the aircraft.
 14. Cooling deviceaccording to claim 11, wherein the heat exchanger (26) is configuredaccording to the counterflow principle.
 15. Cooling device according toclaim 11, wherein the heat exchanger (26) comprises a throttle element(32) for throttling the flow volume of the liquid coolant through theheat exchanger (26).
 16. Cooling device according to claim 15, whereinthe throttle element (32) is a control valve.
 17. Cooling deviceaccording to claim 11, wherein the heat exchanger (26) is provided withan intake (22) and a return (24) for the liquid coolant for connectionto a line system which is installed on board the aircraft, the heatexchanger (26) further comprising a throttle element (32) for throttlingthe flow volume of the liquid coolant through the heat exchanger (26),wherein the throttle element (32) is disposed in the return (24). 18.Cooling device according to claim 17, wherein the throttle element (32)is a control valve.
 19. Cooling device according to claim 11, wherein afan (30) is disposed in the cooling chamber (34).
 20. Cooling deviceaccording to claim 11, wherein the liquid coolant does not undergo aphase transition during operation of the cooling device.
 21. Coolingdevice according to claim 11, wherein the heat exchanger (26) and therefrigerant (28) are configured such that the cooling chamber (34) canbe cooled to a temperature below 0° Celsius.